The present invention relates, in general, to electronics, and more particularly, to methods of forming semiconductor devices and structure.
Previously, various methods and circuit structures were used to form over-voltage and under-voltage protection for circuits. In one application that provided both under-voltage and over-voltage protection, two N-channel metal oxide semiconductor (MOS) transistors were connected in series with their sources tied together at a common point. One example of such an application is disclosed in United States patent publication 2004/0150927 by Strayer et al that was published on Aug. 5, 2004. Such an implementation was difficult to integrate onto a single semiconductor substrate due to parasitic diodes associated with integrated transistors. Consequently, this architecture required using non-integrated transistor. The non-integrated transistors increased the cost of the system that used such an architecture.
Accordingly, it is desirable to have a method of protecting circuits from over-voltage and under-voltage conditions that can be integrated onto a single semiconductor substrate.
For simplicity and clarity of illustration, elements in the figures are not necessarily to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor or a cathode or anode of a diode, and a control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Although the devices are explained herein as certain N-channel or P-Channel devices, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with the present invention. It will be appreciated by those skilled in the art that the words during, while, and when as used herein are not exact terms that mean an action takes place instantly upon an initiating action but that there may be some small but reasonable delay between the reaction that is initiated by the initial action.